[RFC PATCH 09/35] NFSv4.2: define and use extended attribute overhead sizes

[Frank van der Linden <fllinden@amazon.com>]

Define, much like for read and write operations, the maximum overhead
sizes for get/set/listxattr, and use them to limit the maximum payload
size for those operations, in combination with the channel attributes.

Signed-off-by: Frank van der Linden <fllinden@amazon.com>
---
 fs/nfs/internal.h   |  5 +++++
 fs/nfs/nfs42xdr.c   | 23 +++++++++++++++++++++++
 fs/nfs/nfs4client.c | 31 +++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+)

diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index e64f810223be..a1464bf8d178 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -295,6 +295,11 @@ extern const u32 nfs41_maxread_overhead;
 extern const u32 nfs41_maxwrite_overhead;
 extern const u32 nfs41_maxgetdevinfo_overhead;
 #endif
+#ifdef CONFIG_NFS_V4_XATTR
+extern const u32 nfs42_maxsetxattr_overhead;
+extern const u32 nfs42_maxgetxattr_overhead;
+extern const u32 nfs42_maxlistxattrs_overhead;
+#endif
 
 /* nfs4proc.c */
 #if IS_ENABLED(CONFIG_NFS_V4)
diff --git a/fs/nfs/nfs42xdr.c b/fs/nfs/nfs42xdr.c
index d7657be74557..ca29d2702017 100644
--- a/fs/nfs/nfs42xdr.c
+++ b/fs/nfs/nfs42xdr.c
@@ -199,6 +199,29 @@
 				decode_sequence_maxsz + \
 				decode_putfh_maxsz + \
 				decode_removexattr_maxsz)
+
+/*
+ * These values specify the maximum amount of data that is not
+ * associated with the extended attribute name or extended
+ * attribute list in the SETXATTR, GETXATTR and LISTXATTR
+ * respectively.
+ */
+const u32 nfs42_maxsetxattr_overhead = ((RPC_MAX_HEADER_WITH_AUTH +
+					compound_encode_hdr_maxsz +
+					encode_sequence_maxsz +
+					encode_putfh_maxsz + 1 +
+					nfs4_xattr_name_maxsz)
+					* XDR_UNIT);
+
+const u32 nfs42_maxgetxattr_overhead = ((RPC_MAX_HEADER_WITH_AUTH +
+					compound_decode_hdr_maxsz +
+					decode_sequence_maxsz +
+					decode_putfh_maxsz + 1) * XDR_UNIT);
+
+const u32 nfs42_maxlistxattrs_overhead = ((RPC_MAX_HEADER_WITH_AUTH +
+					compound_decode_hdr_maxsz +
+					decode_sequence_maxsz +
+					decode_putfh_maxsz + 3) * XDR_UNIT);
 #endif
 
 static void encode_fallocate(struct xdr_stream *xdr,
diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
index da6204025a2d..d6f28bcd0929 100644
--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -990,6 +990,36 @@ static void nfs4_session_limit_rwsize(struct nfs_server *server)
 #endif /* CONFIG_NFS_V4_1 */
 }
 
+/*
+ * Limit xattr sizes using the channel attributes.
+ */
+static void nfs4_session_limit_xasize(struct nfs_server *server)
+{
+#ifdef CONFIG_NFS_V4_XATTR
+	struct nfs4_session *sess;
+	u32 server_gxa_sz;
+	u32 server_sxa_sz;
+	u32 server_lxa_sz;
+
+	if (!nfs4_has_session(server->nfs_client))
+		return;
+
+	sess = server->nfs_client->cl_session;
+
+	server_gxa_sz = sess->fc_attrs.max_resp_sz - nfs42_maxgetxattr_overhead;
+	server_sxa_sz = sess->fc_attrs.max_rqst_sz - nfs42_maxsetxattr_overhead;
+	server_lxa_sz = sess->fc_attrs.max_resp_sz -
+	    nfs42_maxlistxattrs_overhead;
+
+	if (server->gxasize > server_gxa_sz)
+		server->gxasize = server_gxa_sz;
+	if (server->sxasize > server_sxa_sz)
+		server->sxasize = server_sxa_sz;
+	if (server->lxasize > server_lxa_sz)
+		server->lxasize = server_lxa_sz;
+#endif
+}
+
 static int nfs4_server_common_setup(struct nfs_server *server,
 		struct nfs_fh *mntfh, bool auth_probe)
 {
@@ -1037,6 +1067,7 @@ static int nfs4_server_common_setup(struct nfs_server *server,
 		goto out;
 
 	nfs4_session_limit_rwsize(server);
+	nfs4_session_limit_xasize(server);
 
 	if (server->namelen == 0 || server->namelen > NFS4_MAXNAMLEN)
 		server->namelen = NFS4_MAXNAMLEN;
-- 
2.17.2